I just reinstalled FSX (Deluxe edition) on my new computer. According to the "Win7 compatability center", I need to download a file to make it work with Win7 (64bit). The question is.....do I also need to download the service pack 1, or anything else?

Yes, service pack 1 is a must and 2 resp Acceleration is highly recommended. A survey showed that 70% of my costumors run FSX with Acceleration, so that is the main target and test plattform for any real FSX addon.

There have been reports with registry problems, in that case you need the additional download, but that is in 1 out of 1000 cases.